Long-range correlated dynamics in amorphous selenium

Recent works in supported polymer and organic molecular films have shown that the thin and bulk films exhibit very different average relaxation time due to the influence of the free surface in enhancing the dynamics in layers close to the free surface. When increasing the film thickness to up to 100nm, there exists a transition from liquid-like to glassy behavior. The mid point of the transition for both polymer and organic molecular glasses are found to be \textasciitilde 30nm. We use cooling rate-dependent Tg measurements to demonstrate in this work that an inorganic network glass, amorphous selenium, exhibits the similar enhanced dynamics in thin films. This observation suggests a long-range correlated dynamics in amorphous selenium. The result can help elucidate the origin of enhanced dynamics in thin glasses, and also broaden the existing literatures on correlated dynamics in amorphous thin films.